Spark plugs have been required not only to have an extended service life so as to achieve freedom from maintenance but also to realize enhanced ignition performance and combustion efficiency through reduction in size of electrodes. In order to meet such a requirement, there has been widely used a spark plug in which a noble metal tip formed of platinum, iridium, or the like is joined to a spark discharge portion of a center electrode. Further, in order to further enhance ignition performance, in a proposed technique, a noble metal tip is disposed not only on the center electrode but also on a ground electrode (the external electrode) (see, for example, Japanese Patent Application Laid-Open (kokai) No. 2004-134209).
As proposed in the above-mentioned patent document, the noble metal tip is fixed to the ground electrode through a process in which the noble metal tip is fixed to a member (an intermediate member) different from the ground electrode by means of laser welding, and the intermediate member carrying the noble metal tip joined thereto is joined to the ground electrode by means of resistance welding.